For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningRear Spring Insulator Replacement
Removal Procedure
Raise and suitably support the vehicle. Refer to Lifting and Jacking the
Vehicle.
Support the rear axle with a tall jack stand near the shock absorber.
Remove the lower shock bolt. Refer to Shock Absorber Replacement.
Using the tall jack stands, slowly lower the rear a ...
Recommended Fuel
Use regular unleaded gasoline with a posted octane rating of 87 or higher. If
the octane rating is less than 87, an audible knocking noise, commonly referred
to as spark knock, might be heard when driving.
If this occurs, use a gasoline rated at 87 octane or higher as soon as possible.
If hea ...
Traction Control System (TCS)/StabiliTrak® Light
The StabiliTrak or Traction Control System (TCS) indicator/warning light comes
on briefly when the engine is started.
If the light does not come on, have the vehicle serviced by your dealer.
If the system is working normally, the indicator light turns off.
If the light is on and not flashing, ...